Macro lens system and imaging apparatus

ABSTRACT

A macro lens system includes, in this order from an object side: a positive first lens group; a negative second lens group; a positive third lens group; a negative fourth lens group; a positive fifth lens group; and a negative sixth lens group. The first lens group is constituted by three lenses. The second lens group, the fourth lens group, and the fifth lens group are independently moved in the direction of the optical axes thereof when focusing from an object at infinity to an object at a most proximate distance. The second lens group moves toward the image side and the fourth lens group moves toward the object side when focusing from an object at infinity to an object at a most proximate distance.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims priority under 35 U.S.C. §119 to JapanesePatent Application No. 2014-038242 filed on Feb. 28, 2014. The aboveapplication is hereby expressly incorporated by reference in itsentirety, into the present application.

TECHNICAL FIELD

The present invention is related to a macro lens system suited forelectronic cameras such as digital cameras, video cameras, broadcastcameras, and security cameras, and an imaging apparatus equipped withthe macro lens system.

BACKGROUND ART

There are conventional macro lens systems having close distance imagingat imaging magnification ratios of approximately 1× as their mainpurpose.

These macro lens systems are capable of continuously focusing whenimaging an object at infinity to an object at a most proximate distanceat which the imaging magnification ratio is approximately 1×. The macrolens systems are particularly designed to obtain high opticalperformance during imaging of objects at close distances.

Generally, the floating focus method, in which two or more lens groupsare moved during focusing operations, is employed in order to suppressvariations in aberration accompanying the focusing operations.

Conventionally, the front focusing type of focusing operation, in whichthe lens group most toward the object side is driven forward, had beenutilized. However, in the case that an object at a most proximatedistance is imaged, the lens will approach the object, and thereforeoperability deteriorates. In addition, in the case that a first lensgroup having a large diameter is moved, high speed focusing becomesdifficult because the weight of the first lens group is great. Inaddition, there was a problem that in the case that close distanceimaging at approximately 1× magnification is performed, longitudinalchromatic aberrations become great.

Recently, imaging lenses that adopt the floating focus method, in whicha first lens group is fixed and focusing operations are performed bymoving a plurality of other lens groups, are being employed. Further,focusing methods that move three or more lens groups in order to furthersuppress variations in aberration due to focusing operations have beenproposed in Japanese Unexamined Patent Publication Nos. 2012-058682 and2011-048232.

SUMMARY OF THE INVENTION

However, the macro lenses disclosed in Japanese Unexamined PatentPublication No. 2012-058682 and Japanese Unexamined Patent PublicationNo. 2011-048232 do not sufficiently correct chromatic aberration duringphotography at close distances, and there is demand for a macro lenshaving further improved properties.

The object of the present invention is to provide a macro lens systemhaving an imaging magnification of approximately 1× that favorablycorrects chromatic aberrations even when imaging at close distances, andan imaging apparatus equipped with the macro lens system.

A macro lens system of the present invention consists essentially of, inthis order from an object side:

a first lens group having a positive refractive power;

a second lens group having a negative refractive power;

a third lens group having a positive refractive power;

a fourth lens group having a negative refractive power;

a fifth lens group having a positive refractive power; and

a sixth lens group having a negative refractive power; furthercomprising:

a stop which is fixed during focusing operations provided between thesurface of the second lens group toward the image side and the surfaceof the fourth lens group toward the object side; characterized by:

the second lens group, the fourth lens group, and the fifth lens groupbeing independently moved in the direction of the optical axes thereofwhen focusing from an object at infinity to an object at a mostproximate distance; and

the second lens group moving toward the image side and the fourth lensgroup moving toward the object side when focusing from an object atinfinity to an object at a most proximate distance.

In the macro lens system of the present invention, it is preferable for:

the first lens group to have at least one positive lens; and for

at least one positive lens to satisfy Conditional Formulae (1) and (2)below:N1d<1.65  (1)60.0<ν1d  (2)wherein N1d denotes the refractive index of the positive lens in thefirst lens group with respect to the d line, and ν1d denotes the Abbe'snumber of the positive lens in the first lens group with respect to thed line.

In addition, it is preferable for:

the second lens group to have a cemented lens formed by a negative lensand a positive lens, and to satisfy Conditional Formula (3) below:20.0<ν2dn−ν2dp  (3)

wherein ν2dp denotes the Abbe's number of the positive lens that formsthe cemented lens of the second lens group with respect to the d line,and ν2dn denotes the Abbe's number of the negative lens that forms thecemented lens of the second lens group with respect to the d line.

In addition, it is preferable for:

the third lens group to consist essentially of a single positive lens,and to satisfy Conditional Formula (4) below:ν3d<30.0  (4)

wherein ν3d denotes the Abbe's number of the positive lens of the thirdlens group with respect to the d line.

In addition, it is preferable for the macro lens system to satisfyConditional Formula (5) below:0.5<f3/f<1.5  (5)

wherein f denotes the focal length when focused on an object atinfinity, and f3 denotes the focal length of the third lens group.

In addition, it is preferable for the macro lens system to satisfyConditional Formula (6) below:0.5<f45/f<1.5  (6)

wherein f45 is the combined focal length of the fourth lens group andthe fifth lens group when focused on infinity.

In addition, it is preferable for:

the fourth lens group to have a cemented lens formed by a negative lensand a positive lens, and to satisfy Conditional Formula (7) below:20.0<ν4dp−ν4dn  (7)

wherein ν4dp denotes the Abbe's number of the positive lens that formsthe cemented lens of the fourth lens group with respect to the d line,and ν4dn denotes the Abbe's number of the negative lens that forms thecemented lens of the fourth lens group with respect to the d line.

In addition, it is preferable for:

at least one surface within the first lens group to be an asphericalsurface.

In addition, it is preferable for:

at least one surface within the second lens group to be an asphericalsurface.

It is preferable for:

the total number of lenses that constitute the lens groups that moveduring focusing operations to be 7 or less.

In addition, it is preferable for:

the first lens group to consist essentially of three lenses.

In addition, it is preferable for:

the first lens group to have at least one positive lens; and for

at least one positive lens to satisfy Conditional formulae (1) and (2-1)below:N1d<1.65  (1)65.0<ν1d  (2-1)

In addition, it is preferable for:

the second lens group to have a cemented lens formed by a negative lensand a positive lens, and to satisfy Conditional Formula (3-1) below:25.0<ν2dn−ν2dp  (3-1)

In addition, it is preferable for:

the third lens group to consist essentially of a single positive lens,and to satisfy Conditional Formula (4-1) below:ν3d<26.0  (4-1)

It is preferable for:

the macro lens system to satisfy Conditional Formula (5-1) below, andmore preferably Conditional Formula (5-2) below:0.6<f3/f<1.2  (5-1)0.65<f3/f<1.0  (5-2)

In addition, it is preferable for:

the macro lens system to satisfy Conditional Formula (6-1) below.0.6<f45/f<1.0  (6-1)

In addition, it is preferable for:

the fourth lens group to have a cemented lens formed by a negative lensand a positive lens, and to satisfy Conditional Formula (7-1) below.25.0<ν4dp−ν4dn  (7-1)

An imaging apparatus of the present invention is characterized by beingequipped with the macro lens system of the present invention.

Note that the term “consists essentially of . . . ” means that the macrolens system may also include lenses that practically do not have anypower, optical elements other than lenses such as a stop, a mask, aglass cover, and a filter, mechanical components such as lens flanges, alens barrel, an imaging element, and a camera shake correctingmechanism, in addition to the lenses listed above as constituentelements.

In addition, the surface shapes and the signs of the refractive powersof the lenses are considered in the paraxial region in cases thataspherical surfaces are included.

The macro lens system of the present invention consists essentially of,in this order from the object side: the first lens group having apositive refractive power; the second lens group having a negativerefractive power; the third lens group having a positive refractivepower; the fourth lens group having a negative refractive power; thefifth lens group having a positive refractive power; and the sixth lensgroup having a negative refractive power; further comprises: the stopwhich is fixed during focusing operations provided between the surfaceof the second lens group toward the image side and the surface of thefourth lens group toward the object side; and is characterized by: thesecond lens group, the fourth lens group, and the fifth lens group beingindependently moved in the direction of the optical axes thereof whenfocusing from an object at infinity to an object at a most proximatedistance; and the second lens group moving toward the image side and thefourth lens group moving toward the object side when focusing from anobject at infinity to an object at a most proximate distance. Therefore,the macro lens system can be that which is capable of favorablycorrecting chromatic aberrations even when imaging at close distances.

The imaging apparatus of the present invention is equipped with themacro lens system of the present invention. Therefore, the imagingapparatus is capable of obtaining images having high image quality.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 A collection of sectional diagrams that illustrate the lensconfiguration of a macro lens system according to a an embodiment of thepresent invention (corresponding to Example 1)

FIG. 2 A diagram that illustrates the movement trajectories of each lensgroup of the macro lens system according to the embodiment of thepresent invention (corresponding to Example 1) during a focusingoperation

FIG. 3 A collection of sectional diagrams that illustrate the lensconfiguration of a macro lens system according to Example 2 of thepresent invention

FIG. 4 A diagram that illustrates the movement trajectories of each lensgroup of the macro lens system according to Example 2 of the presentinvention during a focusing operation

FIG. 5 A collection of sectional diagrams that illustrate the lensconfiguration of a macro lens system according to Example 3 of thepresent invention

FIG. 6 A diagram that illustrates the movement trajectories of each lensgroup of the macro lens system according to Example 3 of the presentinvention during a focusing operation

FIG. 7 A collection of sectional diagrams that illustrate the lensconfiguration of a macro lens system according to Example 4 of thepresent invention

FIG. 8 A diagram that illustrates the movement trajectories of each lensgroup of the macro lens system according to Example 4 of the presentinvention during a focusing operation

FIG. 9 A collection of sectional diagrams that illustrate the lensconfiguration of a macro lens system according to Example 5 of thepresent invention

FIG. 10 A diagram that illustrates the movement trajectories of eachlens group of the macro lens system according to Example 5 of thepresent invention during a focusing operation

FIG. 11 A collection of diagrams that illustrate each type of aberrationof the macro lens system of Example 1 of the present invention

FIG. 12 A collection of diagrams that illustrate each type of aberrationof the macro lens system of Example 2 of the present invention

FIG. 13 A collection of diagrams that illustrate each type of aberrationof the macro lens system of Example 3 of the present invention

FIG. 14 A collection of diagrams that illustrate each type of aberrationof the macro lens system of Example 4 of the present invention

FIG. 15 A collection of diagrams that illustrate each type of aberrationof the macro lens system of Example 5 of the present invention

FIGS. 16A and 16B A collection of schematic diagrams that illustrate animaging apparatus according to an embodiment of the present invention

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, embodiments of the present invention will be described indetail with reference to the attached drawings. FIG. 1 is a collectionof sectional diagrams that illustrate the lens configuration of a macrolens system according to an embodiment of the present invention, andFIG. 2 is a diagram that illustrates the movement trajectories of eachlens group of the macro lens system. The macro lens system illustratedin FIG. 1 and FIG. 2 has the same configuration as a macro lens systemof Example 1, to be described later. In FIG. 1 and FIG. 2, the left sideis the object side, and the right side is the image side.

As illustrated in FIG. 1 and FIG. 2, the macro lens system has, in thisorder from the object side along an optical axis Z, a first lens groupG1 having a positive refractive power, a second lens group G2 having anegative refractive power, a third lens group G3 having a positiverefractive power, an aperture stop St, a fourth lens group G4 having anegative refractive power, a fifth lens group G5 having a positiverefractive power, and a sixth lens group G6 having a negative refractivepower. The macro lens system is also equipped with an aperture stop Stwhich is fixed during focusing operations provided between the surfaceof the second lens group G2 toward the image side and the surface of thefourth lens group G4 toward the object side. The macro lens system isconfigured such that the second lens group G2, the fourth lens group G4,and the fifth lens group G5 move independently along the direction ofthe optical axes thereof when focusing from an object at infinity to anobject at a most proximate distance, and such that the second lens groupG2 moves toward the image side and the fourth lens group G4 moves towardthe object side when focusing from an object at infinity to an object ata most proximate distance. Note that the aperture stop St in thedrawings does not necessary represent the size or shape thereof, butindicates the position of the stop along the optical axis Z.

When the macro lens system is applied to an imaging apparatus, it ispreferable for a glass cover, a prism, and various filters such as aninfrared ray cutoff filter and a low pass filter to be provided betweenthe optical system and an imaging surface Sim. Therefore, FIG. 1illustrates an example in which a parallel planar optical member PP isprovided between the lens system and the imaging surface Sim, taking theplacement of such filters into consideration.

Variations in aberration during focusing operations can be suppressedand favorable image focusing performance can be obtained, by configuringthe macro lens system with six groups which are, in this order from theobject side, positive, negative, positive, negative, positive, andnegative, and by independently moving the second lens group G2, thefourth lens group G4, and the fifth lens group G5 in the direction ofthe optical axes thereof during focusing operations as described above.

In addition, variations in lateral chromatic aberration in particularcan be suppressed, because the second lens group G2 and the fourth lensgroup G4 move symmetrically with respect to the aperture stop Stdisposed therebetween.

In addition, it is preferable for the first lens group to have at leastone positive lens, and for at least one positive lens to satisfyConditional Formulae (1) and (2) below. Conditional Formulae (1) and (2)are formulae related to the refractive index and the Abbe's number ofthe positive lens of the first lens group G1. By the positive lenssatisfying Conditional Formulae (1) and (2), it becomes possible toperform well balanced correction of chromatic aberrations during imagingof objects at infinity and during imaging of objects at close distances.Note that more favorable properties can be obtained by the positive lenssatisfying Conditional Formulae (1) and (2-1).N1d<1.65  (1)60.0<ν1d  (2)65.0<ν1d  (2-1)

wherein N1d denotes the refractive index of the positive lens in thefirst lens group with respect to the d line, and ν1d denotes the Abbe'snumber of the positive lens in the first lens group with respect to thed line.

In addition, it is preferable for the second lens group to have acemented lens formed by a negative lens and a positive lens, and tosatisfy Conditional Formula (3) below. Conditional Formula (3) isrelated to the Abbe's number of the cemented lens in the second lensgroup G2. By the second lens group satisfying Conditional Formula (3),it becomes possible to perform well balanced correction of chromaticaberrations during imaging of objects at infinity and during imaging ofobjects at close distances. Note that more favorable properties can beobtained by the second lens group satisfying Conditional Formula (3-1).20.0<ν2dn−ν2dp  (3)25.0<ν2dn−ν2dp  (3-1)

wherein ν2dp denotes the Abbe's number of the positive lens that formsthe cemented lens of the second lens group with respect to the d line,and ν2dn denotes the Abbe's number of the negative lens that forms thecemented lens of the second lens group with respect to the d line.

In addition, it is preferable for the third lens group to be constitutedby a single positive lens, and to satisfy Conditional Formula (4) below.Conditional Formula (4) is related to the Abbe's number of the positivelens in the third lens group G3. By the third lens group satisfying thisconditional formula, it becomes possible to favorably correctlongitudinal chromatic aberration. Note that more favorable propertiescan be obtained by the third lens group satisfying Conditional Formula(4-1).ν3d<30.0  (4)ν3d<26.0  (4-1)

wherein ν3d denotes the Abbe's number of the positive lens of the thirdlens group with respect to the d line.

In addition, it is preferable for the macro lens system to satisfyConditional Formula (5) below. Conditional Formula (5) is related to thepower of the third lens group G3. The power of the third lens group G3can be prevented from becoming too strong, and spherical aberrations canbe favorably corrected, by the value of f3/f not being less than thelower limit of Conditional Formula (5). In addition, the power of thethird lens group G3 can be prevented from becoming too weak, and theouter diameters of the moving lens groups can be kept small, whichresults in weight reduction and high speed focusing operations, by thevalue of f3/f not exceeding the upper limit of Conditional Formula (5).Note that more favorable properties can be obtained by satisfyingConditional Formula (5-1), and more preferably Conditional Formula (5-2)below.0.5<f3/f<1.5  (5)0.6<f3/f<1.2  (5-1)0.65<f3/f<1.0  (5-2)

wherein f denotes the focal length when focused on an object atinfinity, and f3 denotes the focal length of the third lens group.

In addition, it is preferable for the macro lens system to satisfyConditional Formula (6) below. Conditional Formula (6) is related to thecombined power of the fourth lens group G4 and the fifth lens group G5.The power of the fourth lens group G4 can be prevented from becoming toostrong, and variation in aberrations due to focusing operations can besuppressed, by the value of f45/f not being less than the lower limit ofConditional Formula (6). In addition, the amount of movement duringfocusing operations can be reduced, which results in the total length ofthe lens system being prevented from becoming large, by the power of thevalue of f45/f not exceeding the upper limit of Conditional Formula (6).Note that more favorable properties can be obtained by satisfyingConditional Formula (6-1)0.5<f45/f<1.5  (6)0.6<f45/f<1.0  (6-1)

wherein f denotes the focal length when focused on an object atinfinity, and f45 denotes the combined focal length of the fourth lensgroup and the fifth lens group when focused on infinity.

In addition, it is preferable for the fourth lens group to have acemented lens formed by a negative lens and a positive lens, and tosatisfy Conditional Formula (7) below. Conditional Formula (7) isrelated to the Abbe's numbers of the lenses that form the cemented lensin the fourth lens group G4. Longitudinal chromatic aberrations can befavorably corrected from imaging an object at infinity to imaging anobject at a most proximate distance, by the Abbe's numbers of the lensessatisfying Conditional Formula (7). Note that more favorable propertiescan be obtained by the Abbe's numbers satisfying Conditional Formula(7-1).20.0<ν4dp−ν4dn  (7)25.0<ν4dp−ν4dn  (7-1)

wherein ν4dp denotes the Abbe's number of the positive lens that formsthe cemented lens of the fourth lens group with respect to the d line,and ν4dn denotes the Abbe's number of the negative lens that forms thecemented lens of the fourth lens group with respect to the d line.

In addition, favorable correction of aberrations will become possiblewithout increasing the number of lenses by forming at least one surfacewithin the first lens group G1 and within second lens group G2 to beaspherical, which contributes to miniaturization and weight reduction ofthe imaging lens system.

It is preferable for the total number of lenses that constitute the lensgroups that move during focusing operations to be 7 or less. Thereby,the weight of the moving lenses can be reduced, contributing to highspeed focusing operations.

In addition, by forming the first lens group G1 with three lenses, thenumber of lenses having large outer diameters can be suppressed in thefirst lens group G1, which contributes to miniaturization, costreduction, and weight reduction.

In the present macro lens system, a specific preferred material to beplaced most toward the object side is glass. Alternatively, atransparent ceramic material may be employed.

In addition, in the case that the present macro lens system is to beutilized in a severe environment, it is preferable for a protectivemultilayer film coating to be provided. Further, an antireflectioncoating may be administered in addition to the protective coating, inorder to reduce ghost light and the like during use.

In the example illustrated in FIG. 1, the optical member PP is providedbetween the lens system and the imaging surface Sim. Alternatively,various filters, such as a low pass filter or filters that cut offspecific wavelength bands, may be provided among the lenses instead ofbeing provided between the lens system and the imaging surface Sim. As afurther alternative, coatings that have the same functions as thevarious filters may be administered on the surfaces of the lenses.

Next, the numerical values of Examples of the macro lens system of thepresent invention will be described.

First, the macro lens system of Example 1 will be described. FIG. 1 is acollection of sectional diagrams that illustrate the lens configurationof the macro lens system of Example 1, and FIG. 2 is a diagram thatillustrates the movement trajectories of each lens group of the macrolens system of Example 1. Note that the optical member PP is illustratedin FIGS. 1 and 2, as well as FIGS. 3 through 10 that correspond toExamples 2 through 5 to be described later. In these drawings, the leftside is the object side, the right side is the image side, and theaperture stops St illustrated therein do not necessary represent thesize or shape thereof, but indicate the positions of the stops along theoptical axis Z.

Basic lens data of the macro lens system of Example 1 are shown in Table1, data related to various factors are shown in Table 2, data related todistances among the moving surfaces are shown in Table 3, and datarelated to aspherical coefficients are shown in Table 4. Hereinafter,the symbols within the tables will be described with reference to thoserelated to Example 1. The same basically applies to tables related toExamples 2 through 5 as well.

In the lens data of Table 1, surface numbers i (i=1, 2, 3, . . . ) thatsequentially increase with the surface of the constituent element mosttoward the object side being designated as 1 are listed in column Si;the radii of curvature of i^(th) surfaces are listed in column Ri; anddistances between an i^(th) surface and an i+1^(st) surface are listedin column Di. In addition, refractive indices with respect to the d line(wavelength: 587.6 nm) of optical elements j (j=1, 2, 3, . . . ) thatsequentially increase with the optical element most toward the objectside being designated as 1 are listed in column Ndj; and the Abbe'snumbers with respect to the d line (wavelength: 587.6 nm) of j^(th)optical elements are listed in column νdj.

Note that the signs of the radii of curvature are positive in cases thatthe shapes of the surfaces are convex toward the object side, andnegative in cases that the shapes of the surfaces are concave toward theobject side. The basic lens data also include data regarding theaperture stop St and the optical member PP. The word (stop) is indicatedalong with the surface number in the row corresponding to the aperturestop St of column Si. In addition, DD[i] is indicated in the rowscorresponding to surface distances that change when changingmagnification of column Di. In addition, the value in the lowermost rowof column Di indicates the distance between the image side surface ofthe optical member PP and the imaging surface Sim.

Focal lengths f′, back focus values Bf′, F value F Nos. and full anglesof view 2ω for a state when imaging an object at infinity, a state whenimaging an object at an intermediate distance, and a state when imagingan object at a most proximate distance are listed as the data related tofactors in Table 2.

In the basic lens data, the data related to the factors, and the datarelated to the distances among the moving surfaces, degrees are employedas the unit of angles, and mm is employed as the unit of length.However, because optical systems may be proportionately enlarged orreduced and utilized, other appropriate units may be employed.

In the lens data of Table 1, the mark “*” is added to surface numberscorresponding to aspherical surfaces, and numerical values of paraxialradii of curvature are listed as the radii of curvature of theaspherical surfaces. The surface numbers Si of the aspherical surfacesand aspherical coefficients related to the aspherical surfaces arelisted in Table 4 as the data related to aspherical coefficients. Theaspherical coefficients are the values of coefficients KA, A, and Am(m=3, 4, 5, . . . , 20) in aspherical formula (A) below.Zd=C·h ²/{1+(1−KA·C ² ·h ²)^(1/2) }+ΣAm·h ^(m)  (A)

wherein Zd represents the depth of the aspherical surface (the length ofa line drawn from a point of the aspherical surface having a height h toa plane perpendicular to the optical axis that contacts the peak of theaspherical surface), h represents the height (the distance from theoptical axis), C represents the reciprocal of the paraxial radius ofcurvature, and KA and Am represent aspherical coefficients (m=3, 4, 5, .. . , 20).

TABLE 1 Example 1: Lens Data Ri νdj Si (Radius of Di Ndj (Abbe's(Surface Number) Curvature) (Distance) (Refractive Index) Number) 1182.1189 1.25 1.80809 22.76 2 23.5133 5.91 1.49700 81.54 3 −58.0868 0.10*4 25.4930 4.00 1.80139 45.45 5 −145.8843 DD[5] 6 −77.6983 1.10 1.8344137.28 *7 20.0000 2.44 8 −65.9381 0.94 1.51680 64.20 9 23.2572 2.302.00272 19.32 10 47.9624 DD[10] 11 57.1170 3.15 2.00069 25.46 12−96.5771 2.87 13 (stop) ∞ DD[13] 14 −146.7867 2.10 2.00100 29.13 15−50.5656 0.10 16 56.0377 3.83 1.72916 54.68 17 −20.0128 0.95 1.8466623.78 18 33.3059 DD[18] 19 46.0122 3.07 2.00100 29.13 20 −76.7327 DD[20]21 −58.4742 1.00 1.90366 31.32 22 26.8039 1.67 23 29.1424 3.30 1.7725049.60 24 227.3277 1.00 25 ∞ 1.22 1.51680 64.20 26 ∞ 23.39 

TABLE 2 Example 1: Items (related to the d line) β = 0 β = −0.5 β =−0.97 f′ 49.81 Bf′ 25.19 FNo. 2.87 3.30 3.84 2ω[°] 32.2 23.0 16.4

TABLE 3 Example 1: Distances Among Lens Groups DD[5] 1.60 5.56 9.57DD[10] 9.00 5.04 1.03 DD[13] 15.88 7.72 2.19 DD[18] 1.50 3.63 3.80DD[20] 1.70 7.74 13.09

TABLE 4 Example 1: Aspherical Surface Coefficients Surface Number 4 KA1.2223430E+00 A3 −3.6035405E−05 A4 8.7742647E−06 A5 −3.1504332E−06 A63.0714624E−07 A7 −1.6353093E−09 A8 −1.7391527E−09 A9 −3.2922576E−11 A101.9638437E−12 A11 3.0961977E−12 A12 −4.6419074E−14 A13 −3.1708403E−14A14 −1.8644455E−15 A15 5.6612429E−16 A16 −2.3833709E−17 Surface Number 7KA 5.7694954E−01 A3 −7.2961393E−05 A4 3.1230355E−05 A5 −6.5467676E−06 A64.0588512E−07 A7 4.1153931E−08 A8 −5.5366383E−09 A9 1.4942900E−10 A10−8.4960165E−11 A11 1.5208835E−11 A12 −7.0633849E−13 A13 0.0000000E+00A14 0.0000000E+00 A15 0.0000000E+00 A16 0.0000000E+00 A17 0.0000000E+00A18 0.0000000E+00 A19 0.0000000E+00 A20 0.0000000E+00

A through L of FIG. 11 are diagrams that illustrate each type ofaberration of the macro lens system of Example 1. A through D of FIG. 11respectively illustrate spherical aberration, astigmatism, distortion,and lateral chromatic aberration in a state when imaging an object atinfinity. E through H of FIG. 11 respectively illustrate sphericalaberration, astigmatism, distortion, and lateral chromatic aberration ina state when imaging an object at an intermediate distance. I through Lof FIG. 11 respectively illustrate spherical aberration, astigmatism,distortion, and lateral chromatic aberration in a state when imaging anobject at a most proximate distance.

Aberrations having the d line (wavelength: 587.6 nm) as a referencewavelength are illustrated in the diagrams that illustrate sphericalaberration, astigmatism, and distortions related to the d line(wavelength: 587.6 nm), the C line (wavelength: 656.3 nm), and the Fline (wavelength: 486.1 nm) are respectively denoted by solid lines,broken lines, and dotted lines in the diagrams that illustrate sphericalaberration. Aberrations in the sagittal direction and the tangentialdirection are respectively denoted by solid lines and dotted lines inthe diagrams that illustrate astigmatism. Aberrations related to the Cline (wavelength: 656.3 nm) and the F line (wavelength: 486.1 nm) arerespectively denoted by broken lines and dotted lines in the diagramsthat illustrate lateral chromatic aberration. Note that “Fno.” denotes Fvalues in the diagrams that illustrate spherical aberrations, and wdenotes half angles of view in the diagrams that illustrate other typesof aberrations.

Next, a macro lens system of Example 2 will be described. FIG. 3 is acollection of sectional diagrams that illustrate the lens configurationof the macro lens system of Example 2, and FIG. 4 is a diagram thatillustrates the movement trajectories of each lens group of the macrolens system of Example 2. Basic lens data of the macro lens system ofExample 2 are shown in Table 5, data related to various factors areshown in Table 6, data related to distances among the moving surfacesare shown in Table 7, and data related to aspherical coefficients areshown in Table 8. A through L of FIG. 12 are diagrams that illustrateeach type of aberration of the macro lens system of Example 2.

TABLE 5 Example 2: Lens Data Si Ndj νdj (Surface Ri Di (Refractive(Abbe's Number) (Radius of Curvature) (Distance) Index) Number) 1319.8036 1.26 1.80809 22.76 2 23.3772 5.90 1.49700 81.54 3 −51.1372 0.10*4 24.4472 4.00 1.80139 45.45 5 −174.0567 DD[5] 6 −77.7001 1.10 1.8344137.28 *7 20.0000 2.44 8 −49.7917 0.94 1.51680 64.20 9 26.1729 2.302.00272 19.32 10 68.7991 DD[10] 11 99.5677 3.15 2.00069 25.46 12−55.5067 2.87 13 (stop) ∞ DD[13] 14 −105.5167 2.10 2.00100 29.13 15−49.7055 0.10 16 93.5226 3.51 1.72916 54.68 17 −21.3233 0.95 1.8466623.78 18 31.9888 DD[18] 19 39.7142 3.07 2.00100 29.13 20 −77.2366 DD[20]21 −84.7104 1.00 1.92286 20.88 22 40.9693 1.87 23 50.6481 2.02 1.8466623.78 24 200.0001 1.00 25 ∞ 1.22 1.51680 64.20 26 ∞ 24.54 

TABLE 6 Example 2: Items (related to the d line) β = 0 β = −0.5 β =−0.97 f′ 49.86 Bf′ 26.35 FNo. 2.87 3.26 3.81 2ω[°] 32.6 23.6 17.2

TABLE 7 Example 2: Distances Among Lens Groups DD[5] 1.60 5.52 9.57DD[10] 9.00 5.08 1.03 DD[13] 16.09 8.02 2.18 DD[18] 1.50 2.28 2.29DD[20] 1.70 8.99 14.81

TABLE 8 Example 2: Aspherical Surface Coefficients Surface Number 4 KA 6.2713275E−01 A3 −1.3100965E−05 A4  2.9799344E−06 A5 −6.4803649E−07 A6 3.0015874E−08 A7  1.6641095E−09 A8 −9.7963045E−11 A9 −6.3898804E−12 A10−2.2118781E−13 A11 −1.4908567E−14 A12  1.4562963E−14 A13 −1.3443413E−15A14 −9.6920440E−17 A15  2.6235676E−17 A16 −1.2303149E−18 Surface Number7 KA 8.1422423E−01 A3 −2.8440507E−05  A4 6.6484074E−06 A5−1.7128775E−06  A6 −3.6189030E−09  A7 1.0461020E−08 A8 5.5471006E−10 A9−3.8544674E−11  A10 −9.0018810E−12  A11 −7.4316217E−13  A121.1154343E−13 A13 0.0000000E+00 A14 0.0000000E+00 A15 0.0000000E+00 A160.0000000E+00 A17 0.0000000E+00 A18 0.0000000E+00 A19 0.0000000E+00 A200.0000000E+00

Next, a macro lens system of Example 3 will be described. FIG. 5 is acollection of sectional diagrams that illustrate the lens configurationof the macro lens system of Example 3, and FIG. 6 is a diagram thatillustrates the movement trajectories of each lens group of the macrolens system of Example 3. Basic lens data of the macro lens system ofExample 3 are shown in Table 9, data related to various factors areshown in Table 10, data related to distances among the moving surfacesare shown in Table 11, and data related to aspherical coefficients areshown in Table 12. A through L of FIG. 13 are diagrams that illustrateeach type of aberration of the macro lens system of Example 3.

TABLE 9 Example 3: Lens Data Si Ri Ndj νdj (Surface (Radius of Di(Refractive (Abbe's Number) Curvature) (Distance) Index) Number) 1375.2254 1.26 1.84666 23.78 2 23.3466 6.50 1.59522 67.74 3 −59.0220 0.10*4 24.8839 4.08 1.80139 45.45 5 −326.0736 DD[5]  6 −78.7848 1.10 1.8061040.73 *7 20.0000 2.44 8 −47.5574 0.94 1.51742 52.43 9 36.2908 2.301.95906 17.47 10 203.5816 DD[10] 11 799.6875 3.15 1.92286 20.88 12−45.9662 2.87 13 (stop) ∞ DD[13] 14 213.1091 2.10 1.69680 55.53 15−50.7251 0.10 16 112.3316 3.78 1.72916 54.68 17 −27.6530 0.95 1.8080922.76 18 29.9784 DD[18] 19 35.0475 3.32 1.91082 35.25 20 −95.5100 DD[20]21 −74.9946 1.00 1.62588 35.70 22 42.5944 2.80 23 −26.0464 2.00 1.5481445.79 24 −27.0200 1.00 25 ∞ 1.22 1.51680 64.20 26 ∞ 24.78 

TABLE 10 Example 3: Items (related to the d line) β = 0 β = −0.5 β =−0.97 f′ 51.52 Bf′ 26.58 FNo. 2.86 2ω[°] 31.8 23.0 16.8

TABLE 11 Example 3: Distances Among Lens Groups DD[5] 1.60 5.49 9.53DD[10] 9.00 5.11 1.07 DD[13] 13.74 7.34 2.21 DD[18] 1.50 2.44 2.67DD[20] 1.70 7.17 12.07

TABLE 12 Example 3: Aspherical Surface Coefficients Surface Number 4 KA 3.7178373E−01 A3 −1.7637048E−05 A4  6.5167860E−06 A5 −8.1435000E−07 A6 3.0593328E−08 A7  1.6007133E−09 A8 −1.3524488E−11 A9  9.9873108E−12 A10−1.1358488E−14 A11 −2.4655584E−13 A12 −7.3640883E−15 A13 −2.0534193E−15A14  1.6500754E−16 A15  7.2270563E−17 A16 −5.2359779E−18 Surface Number7 KA 8.2109126E−01 A3 −4.2940231E−05  A4 1.1385319E−05 A5−3.6643862E−06  A6 1.2945255E−07 A7 2.7952458E−08 A8 −1.4141157E−09  A9−2.9480815E−10  A10 −1.0116810E−11  A11 6.5937178E−12 A12−3.5391243E−13  A13 0.0000000E+00 A14 0.0000000E+00 A15 0.0000000E+00A16 0.0000000E+00 A17 0.0000000E+00 A18 0.0000000E+00 A19 0.0000000E+00A20 0.0000000E+00

Next, a macro lens system of Example 4 will be described. FIG. 7 is acollection of sectional diagrams that illustrate the lens configurationof the macro lens system of Example 4, and FIG. 8 is a diagram thatillustrates the movement trajectories of each lens group of the macrolens system of Example 4. Basic lens data of the macro lens system ofExample 4 are shown in Table 13, data related to various factors areshown in Table 14, data related to distances among the moving surfacesare shown in Table 15, and data related to aspherical coefficients areshown in Table 16. A through L of FIG. 14 are diagrams that illustrateeach type of aberration of the macro lens system of Example 4.

TABLE 13 Example 4: Lens Data Si Ri Ndj νdj (Surface (Radius of Di(Refractive (Abbe's Number) Curvature) (Distance) Index) Number) 1407.0539 1.26 1.84666 23.78 2 21.9999 6.14 1.59522 67.74 3 −56.5029 0.10*4 23.9551 4.00 1.77250 49.47 5 −233.9538 DD[5]  6 −77.7000 1.10 1.8344137.28 *7 20.0000 2.44 8 −64.1789 0.94 1.51742 52.43 9 25.1498 2.302.00272 19.32 10 61.7220 DD[10] 11 224.9631 3.15 2.00272 19.32 12−47.2617 2.87 13 (stop) ∞ DD[13] 14 −46.6689 2.10 2.00100 29.13 15−34.9986 0.10 16 62.1747 3.94 1.72916 54.68 17 −23.4844 0.95 1.8080922.76 18 31.2044 DD[18] 19 36.7378 3.07 2.00100 29.13 20 −102.4158DD[20] 21 −105.5617 1.00 1.84666 23.78 22 36.7534 2.80 23 48.7900 2.401.51680 64.20 24 200.0000 1.00 25 ∞ 1.22 1.51680 64.20 26 ∞ 24.26 

TABLE 14 Example 4: Items (related to the d line) β = 0 β = −0.5 β =−0.97 f′ 51.51 Bf′ 26.07 FNo. 2.87 3.34 3.87 2ω[°] 31.6 23.2 17.0

TABLE 15 Example 4: Distances Among Lens Groups DD[5] 1.60 5.27 9.13DD[10] 8.58 4.91 1.04 DD[13] 14.81 7.77 2.19 DD[18] 1.50 2.26 2.49DD[20] 1.70 7.98 13.32

TABLE 16 Example 4: Aspherical Surface Coefficients Surface Number 4 KA 2.4730542E+00 A3 −2.2999703E−05 A4 −1.7559895E−06 A5 −5.4519393E−06 A6 8.2498736E−07 A7 −3.4850088E−08 A8 −5.4610562E−09 A9  1.4387583E−10 A10 4.7713075E−11 A11  2.8085693E−12 A12 −2.9992785E−13 A13 −6.3489108E−14A14 −2.4604006E−16 A15  8.9980507E−16 A16 −4.3024936E−17 Surface Number7 KA −3.6681482E−01  A3 −3.6110268E−05  A4 3.3043949E−05 A5−4.6527128E−06  A6 2.2954242E−07 A7 5.1865808E−08 A8 −3.5539331E−09  A9−7.0922502E−10  A10 3.0550926E−11 A11 9.1698822E−12 A12 −6.3291954E−13 A13 0.0000000E+00 A14 0.0000000E+00 A15 0.0000000E+00 A16 0.0000000E+00A17 0.0000000E+00 A18 0.0000000E+00 A19 0.0000000E+00 A20 0.0000000E+00

Next, a macro lens system of Example 5 will be described. FIG. 9 is acollection of sectional diagrams that illustrate the lens configurationof the macro lens system of Example 5, and FIG. 10 is a diagram thatillustrates the movement trajectories of each lens group of the macrolens system of Example 5. Basic lens data of the macro lens system ofExample 5 are shown in Table 17, data related to various factors areshown in Table 18, data related to distances among the moving surfacesare shown in Table 19, and data related to aspherical coefficients areshown in Table 20. A through L of FIG. 15 are diagrams that illustrateeach type of aberration of the macro lens system of Example 5.

TABLE 17 Example 5: Lens Data Si Ri Ndj νdj (Surface (Radius of Di(Refractive (Abbe's Number) Curvature) (Distance) Index) Number) 1863.1374 1.26 1.84666 23.78 2 21.1333 6.04 1.60300 65.44 3 −59.0877 0.10*4 24.0990 4.00 1.80139 45.45 5 −202.0278 DD[5]  6 −85.2550 1.10 1.8013945.45 *7 19.9998 2.44 8 −61.0941 0.94 1.51742 52.43 9 23.9108 2.301.84666 23.78 10 57.0507 DD[10] 11 198.2152 3.15 2.00272 19.32 12−48.1489 2.87 13 (stop) ∞ DD[13] 14 −3208.8965 2.10 1.91082 35.25 15−60.5432 0.10 16 105.8085 3.46 1.77250 49.60 17 −21.9424 0.95 1.8466623.78 18 34.0720 DD[18] 19 38.0120 3.07 1.90366 31.32 20 −81.7497 DD[20]21 −95.8790 1.00 1.80809 22.76 22 35.9067 3.50 23 74.8444 2.00 1.8830040.76 24 200.0037 1.00 25 ∞ 1.22 1.51680 64.20 26 ∞ 23.52 

TABLE 18 Example 5: Items (related to the d line) β = 0 β = −0.5 β =−0.97 f′ 51.12 Bf′ 25.32 FNo. 2.87 3.31 3.83 2ω[°] 31.8 23.4 17.0

TABLE 19 Example 5: Distances Among Lens Groups DD[5] 1.60 5.12 8.87DD[10] 8.31 4.79 1.04 DD[13] 16.11 8.17 2.18 DD[18] 1.50 3.19 3.74DD[20] 1.70 7.96 13.39

TABLE 20 Example 5: Aspherical Surface Coefficients Surface Number 4 KA4.1319383E−01 A3 −1.2447769E−05  A4 5.5607953E−06 A5 −8.2298330E−07  A65.1383807E−08 A7 1.3805599E−09 A8 −2.3445326E−10  A9 −7.8513622E−12  A109.1487665E−13 A11 2.9058233E−14 A12 2.6541350E−14 A13 −2.1048379E−15 A14 −2.7729364E−16  A15 2.2689421E−17 A16 7.5771641E−22 Surface Number 7KA 7.4760887E−01 A3 −3.0841177E−05  A4 9.5268314E−06 A5 −2.3115475E−06 A6 −2.1010866E−08  A7 1.5789565E−08 A8 1.0621441E−09 A9 −5.0458397E−11 A10 −1.5442955E−11  A11 −1.3002081E−12  A12 1.8740459E−13 A130.0000000E+00 A14 0.0000000E+00 A15 0.0000000E+00 A16 0.0000000E+00 A170.0000000E+00 A18 0.0000000E+00 A19 0.0000000E+00 A20 0.0000000E+00

The values of the macro lens systems of Examples 1 through 5corresponding to conditional formulas (1) through (7) are shown in Table21 below. Note that all of the Examples use the d line as a referencewavelength, and the values indicated in Table 21 are obtained at thisreference wavelength.

TABLE 21 Formula Condition Example 1 Example 2 Example 3 Example 4Example 5 (1) N1d < 1.65 1.49700 1.49700 1.59522 1.59522 1.60300 (2)60.0 < v1d 81.5 81.5 67.7 67.7 65.4 (3) 20.0 < v2dn − v2dp 44.9 44.934.9 33.1 28.6 (4) N3d < 30.0 25.5 25.5 20.9 19.3 19.3 (5) 0.5 < f3/f <1.5 0.728 0.722 0.916 0.761 0.761 (6) 0.5 < f45/f < 1.5 0.686 0.7990.678 0.707 0.694 (7) 20 < v4dp − v4dn 30.9 30.9 31.9 31.9 25.8

The above data indicates that all of the macro lens systems of Examples1 through 5 satisfy Conditional Formulae (1) through (7). Therefore, itcan be understood that the macro lens systems of the Examples arecapable of favorably correcting chromatic aberrations even when imagingobjects at close distances.

Next, an imaging apparatus according to an embodiment of the presentinvention will be described. FIGS. 16A and 16B are a collection ofdiagrams that illustrate the outer appearance of an example of amirrorless interchangeable lens camera that employs the macro lenssystem according to the embodiment of the present invention, as anexample of the imaging apparatus according to the embodiment of thepresent invention.

FIG. 16A illustrates the outer appearance of the camera as viewed fromthe front, and FIG. 16B illustrates the outer appearance of the cameraas viewed from the back. The camera is equipped with a camera main body10. A shutter release button 32 and a power button 33 are provided onthe upper surface of the camera main body 10. A display section 36 andoperating sections 34 and 35 are provided on the back surface of thecamera main body 10. The display section 36 is for displaying obtainedimages.

An imaging aperture, into which light from imaging targets enters, isprovided in the central portion of the front surface of the camera mainbody 10. A mount 37 is provided at a position corresponding to theimaging aperture. The mount 37 enables an interchangeable lens 20 to bemounted onto the camera main body 10. The interchangeable lens 20 is alens barrel in which lens members are housed. An imaging element thatoutputs image signals corresponding to images of subjects formed by theinterchangeable lens 20, such as a CCD, a signal processing circuit thatprocesses the image signals output from the imaging element to generateimages, a recording medium for storing the generated images, etc. areprovided within the camera main body 10. In this camera, a pressingoperation of the shutter release button 32 causes a photographyoperation of a single frame of a still image to be executed. Image dataobtained by photography are stored in the recording medium (not shown)within the camera main body 10.

The camera can be miniaturized as a whole by employing the macro lenssystem of the present embodiment as the interchangeable lens 20 of themirrorless interchangeable lens camera. At the same time, images havinghigh image quality, in which chromatic aberrations are favorablycorrected even during imaging at close distances, can be obtained.

The present invention has been described with reference to theembodiments and Examples. However, the present invention is not limitedto the above embodiments and Examples, and various modifications arepossible. For example, the numerical values of the radii of curvature,the surface distances, the refractive indices, the Abbe's numbers, etc.of the lens components are not limited to those exemplified in the aboveExamples, and may be different values.

What is claimed is:
 1. A macro lens system, consisting of, in this orderfrom an object side: a first lens group having a positive refractivepower; a second lens group having a negative refractive power; a thirdlens group having a positive refractive power; a fourth lens grouphaving a negative refractive power; a fifth lens group having a positiverefractive power; and a sixth lens group having a negative refractivepower; further comprising: a stop which is fixed during focusingoperations provided between the surface of the second lens group towardthe image side and the surface of the fourth lens group toward theobject side; characterized by: the second lens group, the fourth lensgroup, and the fifth lens group being independently moved in thedirection of the optical axes thereof when focusing from an object atinfinity to an object at a most proximate distance; and the second lensgroup moving toward the image side and the fourth lens group movingtoward the object side when focusing from an object at infinity to anobject at a most proximate distance, wherein: the fourth lens group hasa cemented lens formed by a negative lens and a positive lens, with thepositive lens being at the side closest to the object side, andsatisfies Conditional Formula (7) below:20.0<ν4dp−ν4dn  (7) wherein ν4dp denotes the Abbe's number of thepositive lens that forms the cemented lens of the fourth lens group withrespect to the d line, and ν4dn denotes the Abbe's number of thenegative lens that forms the cemented lens of the fourth lens group withrespect to the d line.
 2. A macro lens system as defined in claim 1,wherein: the first lens group has at least one positive lens; and atleast one positive lens satisfies Conditional Formulae (1) and (2)below:N1d<1.65  (1)60.0<ν1d  (2) wherein N1d denotes the refractive index of the positivelens in the first lens group with respect to the d line, and ν1d denotesthe Abbe's number of the positive lens in the first lens group withrespect to the d line.
 3. A macro lens system as defined in claim 1,wherein: the second lens group has a cemented lens formed by a negativelens and a positive lens, and satisfies Conditional Formula (3) below:20.0<ν2dn−μ2dp  (3) wherein ν2dp denotes the Abbe's number of thepositive lens that forms the cemented lens of the second lens group withrespect to the d line, and ν2dn denotes the Abbe's number of thenegative lens that forms the cemented lens of the second lens group withrespect to the d line.
 4. A macro lens system as defined in claim 1,wherein: the third lens group consists essentially of a single positivelens, and satisfies Conditional Formula (4) below:ν3d<30.0  (4) wherein ν3d denotes the Abbe's number with respect to thed line of the positive lens of the third lens group.
 5. A macro lenssystem as defined in claim 1, wherein: the macro lens system satisfiesConditional Formula (5) below:0.5<f3/f<1.5  (5) wherein f denotes the focal length of the macro lenssystem when focused on an object at infinity, and f3 denotes the focallength of the third lens group.
 6. A macro lens system as defined inclaim 1, wherein: the macro lens system satisfies Conditional Formula(6) below:0.5<f45/f<1.5  (6) wherein f45 denotes the combined focal length of thefourth lens group and the fifth lens group when focused on infinity. 7.A macro lens system as defined in claim 1, wherein: at least one surfacewithin the first lens group is an aspherical surface.
 8. A macro lenssystem as defined in claim 1, wherein: at least one surface within thesecond lens group is an aspherical surface.
 9. A macro lens system asdefined in claim 1, wherein: the total number of lenses that constitutethe lens groups that move during focusing operations is 7 or less.
 10. Amacro lens as defined in claim 1, wherein: the first lens group consistsessentially of three lenses.
 11. A macro lens system as defined in claim1, wherein: the first lens group has at least one positive lens; and atleast one positive lens satisfies Conditional Formulae (1) and (2-1)below:N1d<1.65  (1)65.0<ν1d  (2-1) wherein N1d denotes the refractive index of the positivelens in the first lens group with respect to the d line, and ν1d denotesthe Abbe's number of the positive lens in the first lens group withrespect to the d line.
 12. A macro lens system as defined in claim 1,wherein: the second lens group has a cemented lens formed by a negativelens and a positive lens, and satisfies Conditional Formula (3-1) below:25.0<ν2dn−ν2dp  (3-1) wherein ν2dp denotes the Abbe's number of thepositive lens that forms the cemented lens of the second lens group withrespect to the d line, and ν2dn denotes the Abbe's number of thenegative lens that forms the cemented lens of the second lens group withrespect to the d line.
 13. A macro lens system as defined in claim 1,wherein: the third lens group consists essentially of a single positivelens, and satisfies Conditional Formula (4-1) below:ν3d<26.0  (4-1) wherein ν3d denotes the Abbe's number of the positivelens of the third lens group with respect to the d line.
 14. A macrolens system as defined in claim 1, wherein: the macro lens systemsatisfies Conditional Formula (5-1) below:0.6<f3/f<1.2  (5-1) wherein f denotes the focal length of the macro lenssystem when focused on an object at infinity, and f3 denotes the focallength of the third lens group.
 15. A macro lens system as defined inclaim 1, wherein: the macro lens system satisfies Conditional Formula(5-2) below:0.65<f3/f<1.0  (5-2) wherein f denotes the focal length of the macrolens system when focused on an object at infinity, and f3 denotes thefocal length of the third lens group.
 16. A macro lens system as definedin claim 1, wherein: the macro lens system satisfies Conditional Formula(6-1) below:0.6<f45/f<1.0  (6-1) wherein f45 denotes the combined focal length ofthe fourth lens group and the fifth lens group when focused on infinity.17. A macro lens as defined in claim 1, wherein: the fourth lens grouphas a cemented lens formed by a negative lens and a positive lens, withthe positive lens being at the side closest to the object side, andsatisfies Conditional Formula (7-1) below:25.0<ν4dp−ν4dn  (7-1) wherein ν4dp denotes the Abbe's number of thepositive lens that forms the cemented lens of the fourth lens group withrespect to the d line, and ν4dn denotes the Abbe's number of thenegative lens that forms the cemented lens of the fourth lens group withrespect to the d line.
 18. An imaging apparatus, comprising: anapparatus body; and the macro lens system defined in claim 1 mounted tothe apparatus body.